Environmental Risk Factors for Prostate Cancer in Overburdened, Understudied Populations

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By Lauren Hurwitz, Ph.D., MHS
2022 Coleman Research Innovation Awardees
National Institute on Minority Health and Health Disparities
Postdoctoral Fellow
National Cancer Institute

Prostate cancer is the second most frequently diagnosed cancer among men globally, and the leading cause of cancer death among men in 48 countries, most of which are in Africa, the Caribbean, and South America1. In the United States, prostate cancer is also the cancer with the largest disparities by race, with incidence rates 60-70% higher and mortality rates 100-120% higher in Black men as compared to non-Hispanic White men2. The underlying drivers of prostate cancer racial disparities are not well understood but likely involve a complex interplay of genetic, social, structural, and environmental factors2.

As a Postdoctoral Fellow at the National Cancer Institute (NCI), I am part of group studying environmental and occupational risk factors for prostate cancer, including how they may be inequitably distributed and contributing to these disparities. Using studies of highly exposed occupational groups in the U.S., we have been investigating pesticide exposure and its potential impact on prostate cancer risk among farmers. Evidence from the Agricultural Health Study, a large prospective cohort study, suggests that specific pesticides (certain organophosphate and organochlorine insecticides) are associated with risk of more aggressive forms of prostate cancer3, 4. Similar associations have been observed in case-control studies as well5. While informative, the prior studies have one major limitation—most studies of pesticides and prostate cancer risk have been conducted in non-Hispanic White populations.

These prior studies indicate that exposure to specific pesticides may increase prostate cancer risk among White men. However, we do not know if these same pesticides also increase risk of prostate cancer among Black men from the U.S., or men from the Caribbean and sub-Saharan Africa, where both exposure to pesticides and prostate cancer incidence and mortality rates are particularly high. Men from different racial and ethnic groups may be exposed to different types or levels of pesticides due to different historical patterns of pesticide use within and across countries, and due to interacting social and structural factors. This was highlighted in the news recently6 in studies from the French islands of Martinique and Guadeloupe—islands with primarily African-descent populations, and some of the highest prostate cancer incidence rates in the world. These studies found a link between prostate cancer risk and chlordecone and the dichlorodiphenyltrichloroethane (DDT) metabolite DDE, organochlorine insecticides that were widely used on these islands7,8, underscoring the need to investigate pesticides and cancer risk across geographically and racially diverse populations.

Sub-Saharan Africa is another region of the world with heavy use of pesticides and a high burden of prostate cancer, yet no epidemiologic studies to date have investigated pesticides and prostate cancer risk among African men9. Exposure to organochlorine insecticides, and specifically DDT and its metabolites, may be particularly high in sub-Saharan Africa; though most countries have now banned the use of DDT for agricultural purposes, many countries in this region still use DDT to combat mosquitos that spread malaria. Like other organochlorine insecticides, DDT is extremely persistent and known to have detrimental effects on the environment, but the human health effects of exposure are not fully understood.

To address this gap, our group initiated a study to measure blood levels of organochlorine insecticides among men with and without prostate cancer from the Greater Accra Region of Ghana. This work is still ongoing, but our pilot results indicate that exposure to DDT in this population is ubiquitous; all samples in the pilot had detectable levels of p,p’- DDE, the primary DDT metabolite, and levels were much higher than those of men from the U.S. Overall, we hope this work will further our understanding of the relationship between pesticide exposures and prostate cancer risk, while shedding light on environmental risk factors that may disproportionately affect overburdened yet understudied populations.

References

  1. Sung, H., et al., Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA Cancer J Clin., 2021. 71(3): p. 209-249. doi: 10.3322/caac.21660. Epub 2021 Feb 4.
  2. Nyame, Y.A., et al., Deconstructing, Addressing, and Eliminating Racial and Ethnic Inequities in Prostate Cancer Care. Eur Urol, 2022. 30(22): p. 01677-3.
  3. Koutros, S., et al., Risk of total and aggressive prostate cancer and pesticide use in the Agricultural Health Study. Am J Epidemiol., 2013. 177(1): p. 59-74. doi: 10.1093/aje/kws225. Epub 2012 Nov 21.
  4. Pardo, L.A., et al., Pesticide exposure and risk of aggressive prostate cancer among private pesticide applicators. Environ Health., 2020. 19(1): p. 30. doi: 10.1186/s12940-020-00583-0.
  5. Koutros, S., et al., Prediagnostic Serum Organochlorine Concentrations and Metastatic Prostate Cancer: A Nested Case-Control Study in the Norwegian Janus Serum Bank Cohort. Environ Health Perspect., 2015. 123(9): p. 867-72. doi: 10.1289/ehp.1408245. Epub 2015 Mar 3.
  6. Whewell, T., The Caribbean islands poisoned by a carcinogenic pesticide, in BBC News. 2020.
  7. Emeville, E., et al., Associations of plasma concentrations of dichlorodiphenyldichloroethylene and polychlorinated biphenyls with prostate cancer: a case-control study in Guadeloupe (French West Indies). Environ Health Perspect., 2015. 123(4): p. 317-23. doi: 10.1289/ehp.1408407. Epub 2014 Nov 21.
  8. Multigner, L., et al., Chlordecone exposure and risk of prostate cancer. J Clin Oncol., 2010. 28(21): p. 3457-62. doi: 10.1200/JCO.2009.27.2153. Epub 2010 Jun 21.
  9. United Nations Environment Programme Chemicals, Regionally Based Assessment of Persistent Toxic Chemicals: Sub-Saharan Africa Regional Report. 2002: Switzerland.
Categories: Scientific Research